To address issues such as the significant variance in shut-in effects between wells and the unclear effectiveness and timeliness of shut-ins during fracturing in shale formations

a numerical model integrating fracturing

shut-in

and production processes was developed. This model considers the synergistic effects of fracture closure

oil-water imbibition replacement

and fracturing fluid retention. The model's reliability was verified through simulations

exploring the oil-water migration law in the formation during the shut-in period of shale oil fractured wells and determining the optimal shut-in duration. Research indicates that: ① The oil-water migration characteristics during well shut-in undergo phased changes over time

which can be categorized into three main control stages: fracture closure

imbibition replacement

and energy balance. Additionally

these migration laws are closely related to the complexity of hydraulic fractures in space. ② Under the influence of capillary imbibition

extending the shut-in time appropriately benefits the initial production of fractured wells. However

an increase in fracturing fluid retention within the matrix can also exacerbate oil phase permeability damage. Based on the law of change in incremental oil volume

a reasonable shut-in time is identified to be between 30 to 45 days. ③ Considering real working conditions

“fracturing well shut-in time” is proposed as an indicator for optimizing well shut-in

which aims to improve time efficiency and reduce differences between wells. This paper proposes an evaluation method and simulation workflow for assessing the well shut-in effects of volume fractured horizontal wells

offering valuable guidance in optimizing the reasonable shut-in time for shale oil fractured wells.